Internal standard for HPLC

I am trying to find a new internal standard for my HPLC method as the old IS seems to be unstable. Everything I have read indicates that the IS should elute AFTER the compound of interest. However, most of the chemically similar compounds to my compound of interest will elute BEFORE my compound. Is it a problem if the IS elutes before the compound of interest? Or is it just important that it elutes near to the compound of interest, without the peaks interfering with eachother?